The field of the invention relates to air/fuel control systems for internal combustion engines.
It is known to adjust a mixture of air and fuel inducted into an engine in response to a feedback variable derived by integrating an output of a two-state exhaust gas oxygen sensor. In such systems, the inducted air/fuel mixture oscillates about a stoichiometric air/fuel ratio. It is also known to modulate the fuel inducted into the engine by a periodic modulation signal to synchronize the aforementioned oscillations.
The inventors have recognized a number of problems with the above approaches. One problem is that an air/fuel transient caused, for example, by accelerator pedal tip-in may cause an air/fuel transient. And such a transient may be exacerbated by the aforesaid modulation signal.